From abc9767034d7c065e6a861cc398a580d0f94e24f Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Sa=C3=BAl=20Ibarra=20Corretg=C3=A9?= <s@saghul.net>
Date: Mon, 25 Mar 2024 11:57:52 +0100
Subject: [PATCH] win: simplify uv_once implementation

* win: simplify uv_once implementation

InitOnceExecuteOnce is available in Windows >= Vista.

Ref: https://learn.microsoft.com/en-us/windows/win32/api/synchapi/nf-synchapi-initonceexecuteonce
---
 include/uv/win.h |  4 ++--
 src/win/thread.c | 44 +++++++++++---------------------------------
 2 files changed, 13 insertions(+), 35 deletions(-)

diff --git a/include/uv/win.h b/include/uv/win.h
index f4adaa21..12ac53b4 100644
--- a/include/uv/win.h
+++ b/include/uv/win.h
@@ -290,8 +290,8 @@ typedef struct {
 #define UV_ONCE_INIT { 0, NULL }
 
 typedef struct uv_once_s {
-  unsigned char ran;
-  HANDLE event;
+  unsigned char unused;
+  INIT_ONCE init_once;
 } uv_once_t;
 
 /* Platform-specific definitions for uv_spawn support. */
diff --git a/src/win/thread.c b/src/win/thread.c
index 57c25e8f..bf39b886 100644
--- a/src/win/thread.c
+++ b/src/win/thread.c
@@ -32,45 +32,23 @@
 #include "uv.h"
 #include "internal.h"
 
-static void uv__once_inner(uv_once_t* guard, void (*callback)(void)) {
-  DWORD result;
-  HANDLE existing_event, created_event;
+typedef void (*uv__once_cb)(void);
 
-  created_event = CreateEvent(NULL, 1, 0, NULL);
-  if (created_event == 0) {
-    /* Could fail in a low-memory situation? */
-    uv_fatal_error(GetLastError(), "CreateEvent");
-  }
+typedef struct {
+  uv__once_cb callback;
+} uv__once_data_t;
 
-  existing_event = InterlockedCompareExchangePointer(&guard->event,
-                                                     created_event,
-                                                     NULL);
+static BOOL WINAPI uv__once_inner(INIT_ONCE *once, void* param, void** context) {
+  uv__once_data_t* data = param;
 
-  if (existing_event == NULL) {
-    /* We won the race */
-    callback();
+  data->callback();
 
-    result = SetEvent(created_event);
-    assert(result);
-    guard->ran = 1;
-
-  } else {
-    /* We lost the race. Destroy the event we created and wait for the existing
-     * one to become signaled. */
-    CloseHandle(created_event);
-    result = WaitForSingleObject(existing_event, INFINITE);
-    assert(result == WAIT_OBJECT_0);
-  }
+  return TRUE;
 }
 
-
-void uv_once(uv_once_t* guard, void (*callback)(void)) {
-  /* Fast case - avoid WaitForSingleObject. */
-  if (guard->ran) {
-    return;
-  }
-
-  uv__once_inner(guard, callback);
+void uv_once(uv_once_t* guard, uv__once_cb callback) {
+  uv__once_data_t data = { .callback = callback };
+  InitOnceExecuteOnce(&guard->init_once, uv__once_inner, (void*) &data, NULL);
 }